The present invention relates in general to the field of wireless telecommunications and in particular to the field of power conservation in the amplification of communication signals.
Systems comprising multiple linear power amplifiers have many applications. For example, multiple-channel, four-module linear amplifier systems are used in cellular-telephone base stations or xe2x80x9ccell sitesxe2x80x9d. Such base stations, or cell sites, are well known and are described, for instance, in George Calhoun, Wireless Access and the Local Telephone Network 128-135 (1992), which is incorporated herein by reference. Such amplifier systems are used within cell sites to amplify multiple radio-frequency (RF) signals of various and differing frequencies, or channels or carriers. Such a system typically comprises a splitter, a plurality of linear amplifier modules, a combiner, a splitter/combiner control functionality, and a monitor and control module. Examples of such a system include the Spectrian MC160A series of multi-carrier power amplifiers and the PowerWave MCA9000-400 series of linear amplification systems.
In such a system, an xe2x80x9cinput signalxe2x80x9d is fed into a splitter. This input signal comprises one or more radio-frequency signals of differing frequencies. In other words, this input signal may be a multiple-channel signal. These radio-frequency signals may be in any desired format or protocol, including Advanced Mobile Phone Service (AMPS), Time Division Multiple Access (TDMA), or Code Division Multiple Access (CDMA) standards. The splitter splits the input signal into two or more resulting signals. The resulting signals contain the same frequencies as the input signal, but the power, or amplitude, of the input signal is equally divided among the resulting signals. The splitter in a typical four-module linear amplifier system, such as the PowerWave MCA9000-400 Series Four Module Linear Amplification System, features four outputs, each of which are coupled to one of four linear amplifier modules. The splitter is configured according to the number of linear amplifier modules that are coupled to the splitter and operational. A splitter/combiner control functionality, embodied by, for example, a microprocessor or shelf logic, monitors the number of amplifier modules that are coupled to the splitter and operational, and configures the splitter and combiner accordingly. In a four-module system in which all four modules are operational, the splitter/combiner control functionality configures the splitter for four-modules such that the splitter splits an input signal into four resulting signals, each of which comprise the same frequency content as the input signal and are one-quarter the power. When the splitter is configured according to three coupled and operational amplifier modules, the splitter splits the input signal into three resulting signals, each of equal power, one-third of the input signal. Similarly, when the splitter is configured for two modules, the splitter splits the input signal into two signals, and when the splitter is configured for one module, the splitter does not split the signal.
Each of the four modules amplifies the signal input to that S module to a desired level. The amplified signals are coupled to a combiner. The splitter/combiner control functionality configures the combiner according to the number of power modules coupled to the splitter and that are operational. Thus, in a four-module system, the splitter/combiner control functionality logic configures the combiner for operation in such a system. Accordingly, the combiner combines the four amplified signals into a single output signal for transmission. Typically, this combined output is fed through antenna interface circuitry to a transmit antenna.
Also in such a system, a monitoring and control device is employed to provide and control operating power to each of the modules, to monitor each of the modules, to activate or deactivate all of the modules, and to notify the operator if the system is operating outside of parameters. This device may also be used to configure and reconfigure the splitter and combiner, together with or in place of the splitter/combiner control functionality.
In the systems used in conventional cellular-telephone cell sites, the monitoring and control device does not activate or deactivate individual power amplifier modules independently. All of the modules are either active or all of the modules are inactive.
The multiple-channel, multiple-amplifier linear amplifier systems employed in conventional cell-sites require considerable power and are consequently expensive to operate. A power supply at a conventional cell-site typically provides power to the system at 24-27 DC Volts and the current needed by the system at the time. The power needed by the system typically varies over time each day according to subscriber use of the system. During peak hours, when subscriber demand is highest, the system may require 1500-2500 Watts. During off-peak hours, the power requirement of the system may be approximately 150 Watts, drastically less than the peak-hours demand.
A large part of the power required to operate a four-module linear amplifier system can be thought of in some respects as overheadxe2x80x94it simply maintains all four of the power amplifier modules in an active state when the system is in operation. During peak hours, all four power amplifiers are often needed to amplify the signals handled by the system. Thus, it is often necessary to maintain all four power-amplifiers in the active state during peak hours. During off-peak hours, however, the system may need only one or two of the power amplifiers modules for sufficient operation. It may thus be that only one or perhaps two of the amplifier modules are required to be active during off-peak hours. Maintaining only the required amplifier modules in the active state would require considerably less overhead power.
As mentioned above, the conventional systems do not provide for control over the activation or deactivation of individual power amplifier modules. Rather, all modules remain in the same operation state at any particular time. For example, in a conventional four-module system, all four modules remain in the active state during both peak and non-peak hours. Thus, because all of the modules are either active or inactive at all times, the power amplifier modules: use more power than is necessary for sufficient operation of the system. Conventional systems accordingly use power inefficiently and are therefore more expensive to operate than necessary.
Linear power amplifier systems accordingly to the present invention include an input line, a splitter, a plurality of linear power amplifier modules, a combiner, and a control functionality. The control functionality configures the splitter and combiner according to the number of active amplifier modules coupled to the splitter. The input line delivers a number of input signals on a number of channels to the splitter, which splits the signals among a number of splitter outputs according to its configuration. Each splitter output is coupled to a linear power amplifier module. The signals allocated to each splitter output are communicated by this connection to the corresponding amplifier module. Each linear amplifier module amplifies the communicated signals, and the output of each module is provided to a combiner. The combiner combines the amplified signals according to its configuration and outputs the combined signal, eventually to a radiator. The control functionality, which may be implemented in a microprocessor, receives signals from the system, evaluates them, and uses them to control the linear power amplifier modules. The control functionality evaluates, among other things, how many linear amplifier modules should be in the active state and how many should be in the inactive state at any particular point in time. This decision may be based upon how many amplifier modules are necessary to carry out the system""s objectives. The control functionality will examine the signals it receives from the system to determine, among other things, the volume of signals the system is currently handling. The control functionality may determine the volume of signals the system is currently handling by evaluating the power level of the signals. The control functionality is programmed to determine how many amplifier modules are needed by the system to amplify the detected volume of signals. In addition, this decision may be based, in part or in whole, upon human intervention, upstream information, and other factors supplied by a common-control module.
Linear power amplifier systems according to the present invention use power more efficiently than conventional systems. Such efficiency allows the operating cost of linear power amplification systems according to the present invention to be lower than the operating cost of conventional systems.
Structural differences between systems according to the present invention and conventional systems include the communications lines facilitating independent control over individual power amplification modules. Structural differences also include the combination of structure embodying a splitter, a combiner, and individually-controlled power amplification modules in a mobile communications cell site.
Systems according to the present invention employ the intelligent control of linear amplifier modules in order to increase power-use efficiency. This intelligent control is made after evaluation of states at one or points within and, if desired, without the system. These states may be a wide variety of types of signals, including CDMA, TDMA, and AMPS. Systems according to the present invention are able to evaluate these one or more types of signals and intelligently control individual amplifier modules according to that evaluation. These systems employ structures which split and combine RF signals.
It is accordingly an object of the present invention to provide a linear power amplifier system that uses power more efficiently than the conventional systems by, among other things, controlling activation/deactivation of individual power amplifiers in a manner that reflects actual required capacity.
It is another object of the present invention to provide a linear power system that intelligently controls multiple power amplifier modules of the system so that individual modules can be placed in the active or inactive state as desired, independent of the state of other modules.
It is a further object of the present invention to provide a mobile communications linear power amplifier that requires less power to operate than conventional mobile communications power amplifiers.
Other objects, features, and advantages of the present invention will be apparent with respect to the remainder of this document.